The overall goal of this project is to elucidate the impact of lipids and food-associated physicochemical changes in the gastrointestinal (GI) tract on intestinal mucus barrier properties. This information will motivate strategies for mucosal barrier control, enabling efficient drug carrier systems (e.g. mucosal vaccines), enhanced nutrition, and potentially inhibited pathogen invasion. Gastrointestinal mucus is a natural hydrogel providing a finely-tuned and amazingly selective barrier, protecting the underlying epithelium from harsh physicochemical changes in the intestinal lumen (e.g. elevations in bile salt concentration, lowered pH), selectively inhibiting microbial transport, and enabling efficient absorption of nutrients and water. Despite the significance of mucus's role and potential implications in health and disease, its barrier properties are relatively poorly understood. Preliminary data indicates that intestinal mucus properties are significantly modulated by food-associated lipids and physicochemical changes associated with food (i.e. changes in pH and [Ca+2 ]). To study these phenomena and enable design of strategies to exploit them for therapeutic purposes, the transport of micro-particulates, model microbes and small molecular weight compounds will be analyzed using multiple particle tracking techniques and a novel application of electron paramagnetic resonance (EPR). Particles, microbes and compounds will be exposed to mucus surfaces in media containing food-associated lipids as well as model fasted state intestinal buffer, at varied pH and Ca+2 concentrations. These analyses will be performed on both native mucus as well as purified mucin gels to provide insight into mucus structural components responding to specific food-associated stimuli. Micro- and macro-rheological analyses performed in parallel will indicate the relative significance of mucus gel structural changes vs. interactions occurring between particles/molecules and gel constituents in observed transport phenomena. Structural changes in mucus gels associated with exposure to food-associated lipids and physicochemical environmental changes will also be examined using advanced microscopic techniques, including quick-freeze deep etch microscopy (QF/DEM). The integrity of colloidal structures formed by food-associated lipids within the mucus layer will be examined using EPR and nitroxide-probe labeled bile salts and lipids, as it is currently not understood whether these structures stay intact within mucus, which could significantly impact the nature of transport through this natural hydrogel. The interdisciplinary research team possesses the expertise required to successfully understand and begin to exploit the impact of lipids on the GI mucus barrier, including the PI, a chemical engineer with expertise in transport phenomena in drug delivery and mucus, a biochemist with expertise in pathogen transport through mucus and mucus theology, a mechanical engineer with expertise in advanced microscopic analysis of biological matrix structure, and a chemist with expertise in electron paramagnetic resonance analysis of small molecule mobility in membranes.